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  1. #1

    Default 1977 26ft silverton engine problems

    I need some help figuring out what is the problem with my 1977 26 ft cabin cruiser with a 10.5 beam. I bought the boat with the 454 mercruiser un repairable. So the Marina I got my boat at, said they could put a 350 mercruiser 1979 in and I would be happy with it.
    No need in getting into the opinion of this marina but things did not work out.
    The 350 engine runs great at a idle and rpm is @1,000 set by the marina. Oh yeah it is a reverse rotation engine with a velvet borge warner V-drive 1to1 ratio straight drive shaft.

    It works fine til you push the throttle into the 4 barrel and then it bogs down and looses speed. I have no information about the boat's performance prior to buying it. The engine is rebuilt from the machine shop which the marina did and they installed the engine and did the wiring.
    what is new?
    crank, cam, piston heads exhaust manifolds and risers, carburetor.
    What is rebuilt
    alternator, starter
    what I know about the boat since I have got it running.
    It has done 24 mph at about 4,000 rpm according to lowrance gen3 with a little room to push it more but at that time was unsure of boat so did not push more. The new carburetor was back firing alot so the marina adjusted it and and finally replaced it with another new one.
    The engine ran good for a very short time then I'd found a water leak in the muffles and had to replace them. Turns out the muffles had no insides and fell apart when removed.
    Since then......no speed can only get about 8 mph and engine had a valve tapping. Marina told me that putting on the new mufflers put back pressure on engine speed. I took the muffles off and put straight hose on and that did not improve the performance.
    Long story short the Marina rebuilt the whole engine.
    I took it out and got up to 19mph at 4,000rpm and that was full throttle with the 4 barrel kicking in but did notice a flat spot but passed threw it.
    now less than 10 hours on the rebuilt engine, it will not let me pass into the secondary on the carburetor just bogs down.

    Does anybody have any ideal what the problem is? I was really expecting the boat to do better than 24mph but now it will only do 9 to 13mph.
    I have put another used carburetor and it did the same thing, so I do not think it is the carb. I feel something has deteriorated but not sure what.
    I am down to the plugs, advance electric timing since it has no points or the transmission is binding up but it seems to run fine til I try to open the secondary .
    Does anybody know how fast the 350 should be able to go?
    The boat weighs about 7,500 and is a V-hull fiberglass.

  2. #2
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,145

    Default Re: 1977 26ft silverton engine problems

    I took it out and got up to 19mph at 4,000rpm and that was full throttle with the 4 barrel kicking in but did notice a flat spot but passed threw it.
    now less than 10 hours on the rebuilt engine, it will not let me pass into the secondary on the carburetor just bogs down.
    Ayuh,.... Sounds like ya got 2 problems,....

    #1, the fuel system isn't workin' right,...
    Start at the tank, 'n work yer way to the carb,....
    I'd start by inspectin' the Contents of the fuel filter for anything but clean fresh gasoline,....

    The 2nd problem is the prop is to big, ya need less pitch to get the motor up to 4800 rpms at Wot,....
    Any Grease is Better,... Than No grease at All....

  3. #3

    Default Re: 1977 26ft silverton engine problems

    Quote Originally Posted by bondo View Post
    Ayuh,.... Sounds like ya got 2 problems,....

    #1, the fuel system isn't workin' right,...
    Start at the tank, 'n work yer way to the carb,....
    I'd start by inspectin' the Contents of the fuel filter for anything but clean fresh gasoline,....

    The 2nd problem is the prop is to big, ya need less pitch to get the motor up to 4800 rpms at Wot,....

    Thank for the response
    both fuel tanks were pressure cleaned and new fuel lines installed. I did check the fuel filter inside the carburetor and it was clean.
    Can I just replace the fuel source as a test and bypass the fuel water separator and send gas straight to the carb fuel line?
    I do feel that the prop is too big but do not know how to find the right size and that was why I had gave so much information on the boat weight and size.

  4. #4
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    9,091

    Default Re: 1977 26ft silverton engine problems

    ............................
    Quote Originally Posted by SeaDuctions View Post
    I need some help figuring out what is the problem with my 1977 26 ft cabin cruiser with a 10.5 beam. I bought the boat with the 454 mercruiser un repairable. So the Marina I got my boat at, said they could put a 350 mercruiser 1979 in and I would be happy with it.
    Have I got this right?
    This marina suggested that replacing a single 7.4L BBC with a 5.7L SBC was going to be OK and that you would be happy with it????



    No need in getting into the opinion of this marina but things did not work out.
    Why not....... it looks like they perhaps took advantage of you!

    The 350 engine runs great at a idle and rpm is @1,000 set by the marina.
    1k rpm idle speed is not acceptable.

    Oh yeah it is a reverse rotation engine with a velvet borge warner V-drive 1to1 ratio straight drive shaft.
    OK..... may we safely assume that this hull and V-drive require a REV RH Rotation engine?
    Was this an arbitrary decision by the marina.... or was the 7.4L BBC also REV RH Rotation?


    It works fine til you push the throttle into the 4 barrel and then it bogs down and looses speed.
    Has anyone verified the Progressive and Total Ignition advance as per OEM specs?

    I have no information about the boat's performance prior to buying it. The engine is rebuilt from the machine shop which the marina did and they installed the engine and did the wiring.
    Which piston profile was used during this over-haul?

    what is new?
    crank, cam, piston heads exhaust manifolds and risers, carburetor.
    What is rebuilt
    alternator, starter
    what I know about the boat since I have got it running.
    It has done 24 mph at about 4,000 rpm according to lowrance gen3 with a little room to push it more but at that time was unsure of boat so did not push more.
    That RPM for that speed seems a bit excessive to me.

    The new carburetor was back firing alot so the marina adjusted it and and finally replaced it with another new one.
    How did the marina adjust the cam followers?
    The 8 stop static procedure is goof proof and should always be used.

    The engine ran good for a very short time then I'd found a water leak in the mufflers and had to replace them. Turns out the mufflers had no insides and fell apart when removed.
    Was this on your dime or their dime?

    Since then......no speed can only get about 8 mph and engine had a valve tapping.
    Not a good sign.

    Marina told me that putting on the new mufflers put back pressure on engine speed.
    This is most likely BS!

    I took the muffles off and put straight hose on and that did not improve the performance.
    Long story short the Marina rebuilt the whole engine.
    Again..... or are you talking about the original over-haul?
    And again..... what piston profile is being used?


    I took it out and got up to 19mph at 4,000rpm and that was full throttle with the 4 barrel kicking in but did notice a flat spot but passed threw it.
    now less than 10 hours on the rebuilt engine, it will not let me pass into the secondary on the carburetor just bogs down.
    Again..... is anyone looking at the ignition advance? NOT BASE advance...... I'm asking about the Progressive and Total advance!

    Does anybody have any ideal what the problem is? I was really expecting the boat to do better than 24mph but now it will only do 9 to 13mph.
    I have put another used carburetor and it did the same thing, so I do not think it is the carb. I feel something has deteriorated but not sure what.
    I am down to the plugs, advance electric timing
    Be very careful if you are not experienced at this!

    since it has no points or the transmission is binding up but it seems to run fine til I try to open the secondary .
    Does anybody know how fast the 350 should be able to go?
    Is this a single station or dual station hull?

    The boat weighs about 7,500 and is a V-hull fiberglass.


    .
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

  5. #5
    Join Date
    Jun 2008
    Location
    Island Heights, NJ,
    Posts
    2,571

    Default Re: 1977 26ft silverton engine problems

    Thats an lot of boat for a 350.... It will work, however you are not likely to be happy with the performance. I assume that the 1:1 tranny is the same as the original engine.... Per my signature block, I'm running the same block but the Volvo drive has a 1.61:1 reduction and I swing a 15x17 prop...on a 23 ft DeepV hull ( more extreme than yours) that has a dry weight of about 4000#. What size prop is on there now and was it changed from the 454 setup? Where are you located?
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280
    1972 22ft Bristol
    Honda 7.5HP 4 stroke Long shaft

  6. #6

    Default Re: 1977 26ft silverton engine problems

    Quote Originally Posted by sandkicker View Post
    Thats an lot of boat for a 350.... It will work, however you are not likely to be happy with the performance. I assume that the 1:1 tranny is the same as the original engine.... Per my signature block, I'm running the same block but the Volvo drive has a 1.61:1 reduction and I swing a 15x17 prop...on a 23 ft DeepV hull ( more extreme than yours) that has a dry weight of about 4000#. What size prop is on there now and was it changed from the 454 setup? Where are you located?
    It is a 1:1 v-drive tran with a 18rh17 4 blade. Do you know about how fast I can go once I get it running right?
    i have seen 24 but right now it is topped out at 15.
    I was expecting maybe 25 or higher and cruise somewhere in the 18 range at 3200.
    what pitch do I need.

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